Pipes and tubing are used to carry a variety of fluids, some are liquids and others are gases. These fluids may be under substantial pressures or at standard pressure. Therefore, pipes and tubing are rated according to the fluid pressures which the conduit can carry without rupturing. A particular conduit is considered to be a pipe or tubing depending upon the wall thickness of the conduit, the industry or application in which it is being used, and sometimes upon whether it is plastic or metal. For present purposes and simplicity I will used the term pipe to encompass both pipe and tubing as those terms are used by those skilled in the art.
In hydraulic connections it is quite common to utilize pipes in which the end of the pipe has been flared to form a collar which is placed to abut against a surface of the device to which the pipe is being connected. In order to create the flared end or collar it is customary to provide a clamping die which is pressed against the pipe to be flared at a specified distance away from the end of the pipe. This die typically will have a gripping surface containing teeth or threads which bite into the exterior surface of the pipe being held. The die is pressed against the end of the pipe to hold the pipe during flaring. The flaring process is performed by a flaring machine having an eccentric cone. That cone is pressed against the end of the pipe and rotated circumferentially about the end of the pipe to form a flare. The flare can be at any angle relative to the side of the pipe. For many applications a flat end seal is desired in which case the flare will be at a right angle relative to the exterior surface of the pipe. This pipe flaring practice is quite old, but there have been improvements in the flaring tools. An improved flaring tool and method of using the same for forming a transverse collar on the end of the metal pipe is disclosed in U.S. Pat. No. 4,905,492.
The dies used for clamping the metal ends of the pipe to be flared are quite expensive. Additionally, the clamping action against the pipe being held causes wear, particularly on the gripping surfaces of the dies. When those surfaces have become sufficiently worn the pipe being grasped will slip. Then the surface must be refinished or the die must be scrapped. A second problem with this practice is that a separate set of dies must be made for each diameter of pipe. Consequently, there is a need for a device which can be used in the flaring of pipe ends that will improve die life and enable one to use a single clamping die for holding pipes of more than one diameter.
The art has used rings in couplings for flared and straight pipe. Some of these rings have teeth on the inside surface which will bite into the pipe as a nut or collar is drawn over the ring. Often, the exterior surface of the ring and the mating interior surface of the nut or collar are sloped so that the ring will be pressed against the pipe as the nut or collar are advanced. Examples of this type of coupling can be found in U.S. Pat. Nos. 2,165,621 to Donahue et al., 2,269,629 to Kreidel, and 4,809,418 to Burli. Today, this type of ring is most commonly used for plastic pipe. Whenever such rings have been used on flared pipe the ring has not been used in any way for or during the flaring process. Furthermore, most of the couplings which utilize such rings for plastic pipe contain rings which are not suitable for metal pipe.